The invention relates to an electronic power circuit, and more particularly to an electronic power circuit with low forward and switching losses for a trigger device.
Among electronic power circuits are converter circuits, such as a self-commutated converter which can be operated as an inverter or a rectifier, or a DC/DC converter which can be implemented as a buck converter and/or a boost converter or as part of a switched mode power supply. All these electronic power circuits have in common that they include at least one power semiconductor which is controlled by a corresponding trigger device. To supply a corresponding control current and/or control voltage, the trigger device is connected to outputs of a current supply. The current supply can be connected to a single-phase or multi-phase power network or to a voltage link capacitor of a converter circuit.
Electronic power circuits operate in a voltage range above 100 V. Self-blocking semiconductor are used exclusively as power semiconductors in this voltage range. These self-blocking semiconductors have in common that they are blocking at a control voltage of 0 V. In other words, the self-blocking semiconductor conducts current only when the control voltage exceeds a certain positive value. The self-blocking design of the semiconductors can require a fairly high forward voltage, which during operation can cause forward losses as well as switching losses. Cooling devices may have to be employed to remove the heat dissipation which is partially caused by the self-blocking design of the semiconductors. This increases the required installation space for an electronic power circuit; moreover, electronic power circuits may therefore not be installed in close proximity of other devices that dissipate heat.
The forward losses and switching losses increase with the voltage applied to the power semiconductor. At very high voltages, for example voltages close to 5 kV, only self-blocking bipolar semiconductor switches made of silicon are used for commercially available electronic power circuits.
German Pat. No. DE 196 10 135 C1 discloses a hybrid-power-MOSFET with a self-blocking n-channel MOSFET, in particular a low voltage power MOSFET, and a self-conducting n-channel junction MOSFET. This junction-FET with a high blocking voltage is also referred to as Junction Field Effect Transistor (JFET). These two FETs are connected in series in such a way, that the source terminal of the junction-FET is electrically connected to the drain terminal of the MOSFET and the gate terminal of the junction FET is electrically connected to the source terminal of the MOSFET. This electrical connection of two semiconductor components is typically referred to as cascaded or series connection. The MOSFET with a low blocking voltage of this series connection has an internal bipolar diode which is connected antiparallel to the MOSFET and is generally referred to as reverse or internal free-wheeling diode. The self-blocking n-channel MOSFET of this hybrid power MOSFET is made of silicon, whereas the self-conducting n-channel JFET is made of silicon carbide. This hybrid power MOSFET is designed for a high blocking voltage in excess of 600 V and exhibits only small forward losses.
This hybrid power MOSFET which is self-blocking can hence replace the bipolar semiconductor switches made of silicon used in the aforedescribed electronic power circuits, without requiring changes in the electronic power circuits. This hybrid power MOSFET is made of two semiconductor chips and therefore takes up a relatively large surface area. This not only increases the space requirement of the electronic power circuit, but also its cost.
It would therefore be desirable and advantageous to provide an improved electronic power circuit for a trigger device, which obviates prior art shortcomings and is able to specifically further reduce forward losses and switching losses, without increasing the cost.